@Entity
@Table(name="events")
public class Event {
   
@Id
@Column(name="event_id")
private int id;

private String title;
   
   public Event(){
      this.id = 0;
      this.title = new String();
   }
   
   public Event(int id, String title) throws EmptyDataException{
   if (title=="") throw new EmptyDataException();
         //this.id = id;
         this.title = title;
   }

   public int getId(){
      return this.id;
   }
   
   public void setId(int id){
      this.id = id;
   }
   
   public String getTitle(){
      return this.title;
   }
   
   public void setTitle(String title){
      this.title = title;
   }
   
}

@Entity
@Table(name="USER")
public class User {
   @Id @GeneratedValue
   @Column(name="user_id")
   private int id;
   
   private String name;
   private String address;
    @ManyToMany(targetEntity=Event.class)
   private Set events = new HashSet();
   
   public User(){
      this.id = 0;
      this.name = new String("");
      this.address = new String("");
   }
   
   public User(String name, String address) throws EmptyDataException{
   
   if (name=="" || address==""){
      throw new EmptyDataException();
   }
   
   else {
      //this.id = id;
      this.name = name;
      this.address = address;
      }
   }

   public void setId(int id){
      this.id = id;
   }

   public int getId(){
      return this.id;
   }

   public void setName(String name){
      this.name = name;
   }
   
   public String getName(){
      return this.name;
   }
   
   public void setAddress(String address){
      this.address = address;
   }
   
   public String getAddress(){
      return this.address;
   }
   
   public void setEvents(Set events){
      this.events = events;
   }

   public Set getEvents(){
      return this.events;
   }
   
}

User newUser = new User(request.getParameter("name"), request.getParameter("address"));
session.persist(newUser);